In the Gulf of Mexico, nature’s janitors are hard at work, mopping up the aftermath of a man-made disaster. On 20 April, 2010, an explosion at the Deepwater Horizon rig unleashed the largest oil spill in US history. Now, a team of American scientists led by Terry Hazen have shown that just a month or so after the incident, a microscopic clean-up crew had already started to digest the mess.

The ocean is home to many groups of bacteria that can break down the chemicals found in crude oil. Some, like Alcanivorax, are oil-eating specialists that are usually found in low numbers, only to bloom when oil spills provide them with a sudden banquet. That’s exactly what has happened in the Gulf of Mexico. Hazen has found that these oil-eaters have swelled in number in the contaminated waters.

Just last week, Richard Camilli from the Woods Hole Oceanographic Institution confirmed that after the explosion, a deep plume of oil the size of Manhattan had persisted for several months in the Gulf of Mexico. Camilli also found that oxygen levels near the plume had remained relatively stable. On the bright side, this was good news for local ocean life for a lack of oxygen would create inhospitable dead zones. But it also suggested that bacteria weren’t breaking down the plume as hoped; if they were, you’d expect to see a fall in oxygen levels.

This evidence was, of course, indirect. Hazen’s team actually looked for oil-eating bacteria themselves rather than just signs of their presence, and their report is more optimistic. Using two ships, they collected samples of water near the broken well between 25 May and 2 June. They discovered the same deep-sea oil plume that Camilli did, around 1,100 metres below the surface, and they found that oxygen levels inside the plume were slightly lower than those outside it. But more importantly, they also found twice as many bacteria within the oily cloud.

Sixteen groups of bacteria were enriched within the plume, particularly the Oceanospirillales (a group that includes Alcanivorax who we’ve already met). All sixteen groups have members that can digest the hydrocarbons in oil and can do so in very cold environments where most bacteria would grind to a halt. These plume bacteria were genetically distinct from those outside and no factor except the presence of oil – not temperature or salinity or pressure – could account for this split.

This separation suggested that the microbes of the Gulf had already started to respond to the spill, and their genes sealed the case. Hazen detected the presence of over 1,600 genes involved in breaking down oil, many of which were much more active within the plume. And the worse the contamination, the more active these genes were.

Hazens’ results suggest that the deep ocean has its own janitorial crew that is standing by to mop up the threat of oil contamination. These bacteria have had millennia to practice their art, as oil frequently leaks from natural seeps in the area. They have also evolved to tolerate chilly temperatures, for the depths where the plume exists are at a frosty 5 degrees Celsius. These microscopic cleaners could play a big role in deciding the ultimate fate of the Deepwater Horizon spill.

Hazen estimated that the bacteria were breaking up the oil hydrocarbons faster than they would naturally degrade. Their job might be easier because the plume is relatively dispersed, so the oil particles are smaller and easier to break down. Indeed, Hazen says, “The deep plume has not been detectable for the last 2-3 weeks. It went away fairly rapidly after the well was capped beginning July 12, 2010.”

Nonetheless, there is no room for complacency. Effective though the bacteria are, the oil contains some components that they simply won’t be able to break down and the sheer scale of the spill cannot be taken lightly. As Camilli says, “The long-term ecological implications… remain uncertain and I don’t think anyone could rightly argue that dumping 4.1 million barrels of oil into the Gulf of Mexico was ecologically beneficial.”

Comments (29)

@Ed Yong: Do you know if the highlighted bacteria become part of the food chain in any appreciable way. I can imagine that the increase in bacteria will eventually beget an increase in food chain activity, which could be a boon for the local fisheries.
Also, I would love to get any info on the other stuff that spewed out of the well alongside the crude oil. Have there been any studies on the levels of other contaminants since the spill?

When I wrote about this a while ago (http://tinyurl.com/289ucoh) there was concerns for biodiversity as the bacterial population explosions can completely upset the trophic levels in the environment. Apparently there was a concern that the oily water could destroy photosynthetic plankton numbers and the bacterial population explosion in the oil plumes could act to drive an increase in jellyfish numbers which can feed off the bacteria. These two changes alongside many others would result in a complete shift in the ecosystem.
Are you aware of any new data on plankton and jellyfish numbers or was this just fear-mongering while the leak was still out of control?

I haven’t been following this too closely, so the answer is no. But (a) that doesn’t mean that there is no data and (b) if there is no data, that doesn’t automatically mean that concerned statements are “fear-mongering”. It is perfectly natural to be fearful about what is happening.

Reports are that millions of gallons of “dispersant” was mixed into the oil. That would include old stocks of the extremely toxic Corexit EC9527A, and lots more of the supposedly less toxic EC9500. Producers of “Dispersit” report BP buying millions of gallons of their product, supposedly much less toxic than the Corexits. Oddly, toxicity of these substances is only quoted for arthropods, two of them: silverfish and shrimp.

I wonder how good that “4.1 million barrels” figure is, considering how dishonest BP was, for months, about how much oil was blasting out. The last figure I heard was “up to 60K bb/day”, which seems to suggest closer to 6 million barrels, or 250 million gallons. If they also put in 60K gallons of Dispersit every day, plus a perhaps similar amount of Corexit, that’s well over 2% of the total volume of the plumes. One wonders what effect that stuff has on the bacteria and the food chain.

Also biologists tend not to like the phrase “higher forms of life”. It implies that there’s some sort of ladder where in fact, all modern forms of life are on the same level. Some more complex than others, perhaps, but still on the same level.

Concerning fungi: would you English-speaking people decide how to pronounce it?! Paul Stamets says “fan-juy”, others say “fan-guy”; some say the final i as in pit, others as in spite. I am already struggling to adapt to the barbarian – English – pronunciation of Latin (which means I have to scrap off all pronunciation rules I learned studying it at school), would you barbarians at least reach some consensus on such a simple word as fungi?
Now, to the article:
““and I don’t think anyone could rightly argue that dumping 4.1 million barrels of oil into the Gulf of Mexico was ecologically beneficial.””. No, but some will say “See, problem solved, that wasn’t so bad, was it? Let’s keep drilling everywhere as if nothing happened”. I am not saying that Hazen’s findings should not be made known, of course! But caution will be needed in presenting them, because I fear there are many politicians and businessmen out there ready to mispresent them and drive public opinion to think that nothing really bad happened. As long as scientific findings are divulged by such competent communicators as Ed no worries, but I have already heard in a report on Italian television that the spill’s effects are over (because, apparently, in Lousiana they fished lobsters without any sign of contamination)…
PS I have never seen a paper with so many authors!

According to the expert interviewed all that is needed is fertilizer to get the most out of the process. The link above also links to information on the experts/research team and a scientific paper on the bacteria.

Yeah, I asked about getting the most out of the process. Hazen said that there was no need because the plume had already mostly gone. Camilli said that some people have considered using iron as a fertiliser, but he “would suggest a precautionary principle, because we do not understand the risks and consequences of such manipulations.”

Wow, remarkable that Discover publishes this article without even mentioning that BP funded this study. Are massive conflicts of interest no longer newsworthy?

The institute that funded this study, the Energy Biosciences Institute, is funded by a 10-year, $500 million grant from BP. Not only that, but BP controls 4 of 8 members of the institutes Governance Board.

So, surprise, BP has funded a “scientific” study that says that it’s perfectly natural for all this oil to be in the Gulf, there were already microbes there, ready to eat up all the oil. Problem solved! Isn’t nature great?

But seriously, the bias in this situation is inexcusable. This study is presented as independent, but this conflict of interest is enormous. Doesn’t Discover check these things?

these bacteria evolved in an environment without those. It is impossible to predict the effect of an artificial dispersant which so deeply affects the digesting process.
The dispersant may in fact kill the oil eating bacteria.

who has done tests?

The dispersant as it has been described by biologists effectively allow oil which would not otherwise be able to cross biological cell barriers to pass right through those barriers and enter the system of animals much more quickly.

Furthermore if the bacteria eats the oil does that also mean it eats the attach dispersant molecule or do the bacteria in effect act as a dispersant concentrator leaving higher and higher levels of dispersant in less and less oil filled waters?

@ Brian. A fair point, and thanks for pointing it out. I don’t read press releases and in the paper, all it says about funding is this:

This work was supported by a subcontract from the University of California at Berkeley, Energy Biosciences Institute to Lawrence Berkeley National Laboratory under its U.S. Department of Energy contract DE-AC02- 05CH11231, and by the University of Oklahoma Research Foundation. The SR-FTIR work was conducted at the infrared beamline at the Advanced Light Source which is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy.

But you’re arguing against a straw man. Who exactly said “it’s perfectly natural for all this oil to be in the Gulf, there were already microbes there, ready to eat up all the oil. Problem solved! Isn’t nature great?”

Yes, there are natural seeps. Yes, the microbes are eating it. This is not unexpected given the well-documented activity of oil-eating microbes. This doesn’t mean that flooding the Gulf with oil is a good idea or that the problem is solved. Neither the paper nor my piece suggest this. In fact, I specifically say that there is no room for complacency.

@Vivzizi – This is what Hazen had to say to me on dispersants: “The Dispersants used in deep-sea injection at the well head was a first and the effects we are still sorting out but it looks like it may have contributed to this deep-sea plume or should we say diffuse cloud of droplets of oil (10-60µm), so it appears to have been effective in keeping the oil from easily rising to the surface and this may have both pros and cons.”

The bacteria should probably be harvested, cultured, and used to solve problems with plastic in our landfills. Those bacteria should be able to break up polymerized hydrocarbons if they can digest crude oil.

Gee, how nice these lovely hardworking bacteria, eating away all nesty rude and crude oil . . . we’re so proud of them . . . but, wait. How long will they take to finish the job? Let us suppose, some 100thsd years? Great! Can’t Obama and BP find something that works a bit faster?

does everyone really believe that there is bacteria that all of the sudden has eaten up millions of thick black sticky oil. i don’t, i know for a fact that one of the major ways oil companies make it look like they cleaned it up oil dispersing and guess what that is dish-washing detergent what happens to the oil on your pots and pans when u wash them it is dispersed but it is still there . and if there are so many of these bacteria why weren’t there any up in Alaska or are they only in the gulf

interesting indeed
i little believed when my frind said about it
it would be great if it could be some how used to lessen oil spill itself or break oil down while being spilled in oceans by some how harvesting the bacteria around the tankers or something.